1. Field of the Invention
The present invention relates generally to earth working equipment, and in particular a tubular soil auger for creating a cylindrical hole in the ground.
2. Description of the Related Art
A cylindrical cutting tool that rotates along a central vertical axis enables a user to create a cylindrical hole. A solid cylindrical tool, such as a drill bit, removes a volume of material displaced by the volume of the tool. The larger the cross-section of the solid tool, the larger the diameter of hole that may be created. However, solid tools with a large volume are inherently limited in their utility and the types of machines that can effectively provide enough torque to rotate the tool and create a hole. A hollow, rotating tubular cutting tool may be used to create cylindrical holes having a large diameter by only removing material at the periphery of a plug of the material that is later removed to create the hole. Because the tubular cutting tool itself is cutting or removing little material relative to the volume of material or plug that may be removed, such tools may be used in a wide variety of settings with machines that have low torque or operate at high speeds. However, with tubular tools, if the mass of the tool is not equally balanced, distributed, and aligned along the central vertical axis of the tool, rotation of tool at high speed makes the tool susceptible to wobbling or shaking resulting in damage to the tool, machine, or operator, or difficulty forming a clean hole.
Cylindrical cutting tools are often connected to a power source by an elongated shaft. Typically, the shaft connects to the top of the cylindrical cutting tool at one contact point requiring straightening or truing of the tool and shaft to ensure the tool does not wobble or shake during use causing damage to the power source or operator.
The design and manufacture of tubular cutting tools often involves removal of material from the tool to decrease the mass of the tool, and to facilitate removal of the plug. However, conventional methods of manufacture employ die presses to remove material that can distort the roundness of the tubular wall thereby affecting the balance and distribution of mass of the tool. As a result, such tools are susceptible to wobbling and shaking during use, and have difficulty forming clean holes.
What is needed is a tubular cutting tool that may be rotated at high speed without wobbling or shaking about the central vertical axis of the tool, and a manufacturing method that produces tubular cutting tools that are relatively free from such wobbling or shaking without need of after welding truing or straightening.
Heretofore there has not been available a tubular cutting tool or tubular cutting tool manufacturing method with the advantages and features of the present invention.